The yeast tumor suppressor homologue Sro7p is required for targeting of the sodium pumping ATPase to the cell surface.

• The SRO7/SOP1 encoded tumor suppressor homologue of Saccharomyces cerevisiae is required for maintenance of ion homeostasis in cells exposed to NaCl stress. Here we show that the NaCl sensitivity of the sro7Delta mutant is due to defective sorting of Ena1p, the main sodium pump in yeast. On exposure of sro7Delta mutants to NaCl stress, Ena1p fails to be targeted to the cell surface, but is instead routed to the vacuole for degradation via the multivesicular endosome pathway. SRO7-deficient mutants accumulate post-Golgi vesicles at high salinity, in agreement with a previously described role for Sro7p in late exocytosis. However, Ena1p is not sorted into these post-Golgi vesicles, in contrast to what is observed for the vesicles that accumulate when exocytosis is blocked in sec6-4 mutants at high salinity. These observations imply that Sro7p has a previously unrecognized role for sorting of specific proteins into the exocytic pathway. Screening for multicopy suppressors identified RSN1, encoding a transmembrane protein of unknown function. Overexpression of RSN1 restores NaCl tolerance of sro7Delta mutants by retargeting Ena1p to the plasma membrane. We propose a model in which blocked exocytic sorting in sro7Delta mutants, gives rise to quality control-mediated routing of Ena1p to the vacuole.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Keyword

Adenosine Triphosphatases

metabolism

Carrier Proteins

metabolism

Cation Transport Proteins

metabolism

Cell Membrane

drug effects

metabolism

Gene Expression

drug effects

Genes

Fungal

Golgi Apparatus

drug effects

Mutation

genetics

Protein Transport

drug effects

Recombinant Fusion Proteins

metabolism

Saccharomyces cerevisiae

cytology

drug effects

growth & development

ultrastructure

Saccharomyces cerevisiae Proteins

metabolism

Secretory Vesicles

drug effects

Sequence Homology

Sodium Chloride

pharmacology

Thermodynamics

Tumor Suppressor Proteins

metabolism

Vacuoles

metabolism

Adenosine Triphosphatases/*metabolism

Publication and Content Type

ref (subject category)

art (subject category)